Composite articles and abrasive belts or sheets



Patented Sept. 5, 1944 Q COMP OSITE ARTICLES AND ABBASIVE BELTS ORSHEETS Byron J.' Oakes, 'St. Paul, Minn., assignor to Minnesota Mining &Manufacturing Company, St. Paul, Minn., a corporation of Delaware NoDrawing.

11' Claims.

an article involving a plurality of different lay-' ers of material inintegral, adhering or contiguous relation.

While the present inventionhas other embodiments, as will be understoodfrom the application taken as a whole, one important adaptation is asheet abrasive article, which may be in the form of an abrasive belt orin other form, in which a grit-bonding or binder .coat is Joined inintegral and/or contiguous relation with or is adhesively joined to abacking coat or an impregnated backing material. Where the sheetabrasive article includes a fibrous material, e. g. a fabric backing,one coat may serve to impregnate the fibrous or like material and thenthe binder or grit-bonding coat may be adjacent to and joined inintegral relation with the impregnated fibrous backmg.

The present application is a continuation-inpart of my copendingapplication SerialNo. 558,-

872, filed August 24,- 1931, and also is a continuation-in-part of myapplications Serial Nos. 222,490 and 228,188, filed respectively onAugust 1, 1938, and on September 2,1938. This application is also acontinuation-in-part of the application of Joseph H. Kugler and myself,Serial No. 237,760 filed October 29, 1938.

It is an object of this invention to produce an abrasive or otherarticle which is resistant to deterioration, as, for example, when itcomes into contact with aqueous or other fluids. Another object is toprovide an article which will resist disintegration when subjected to.flexing and/or stresses. Another object is to produce a sheet abrasivearticle having good heat resistance, A further object, where cloth,paper or other fibrous material is employed, is to avoid weakening,rotting, disintegration or other deterioration of such fibrous material.to provide an article comprising two or more layers of material whichare joined together with a strong bond, for example to form a flexibleabrasive article or abrasive belt which can be used wet in the"sanding," abrading or smoothing of glass, Carrara," Vitrolite," marble,plastics, steel, etc. A still further object is to improve the bondbetween a fibrous sheet and a grit-bonding or other coating, as the casemay be, by first giving the fibrous sheet an impregnating treatment orapplying thereto a backing coat of a different Application September 2,1939, Serial No. 293,192 Y A further and salient object is belts andlike articles of improved quality, These and other objects andadvantages will appear from this application taken as a whole.

Illustrative of articles within the scope of this invention are abrasivebelts of an improved type and construction. Abrasive belts known to me,which were in use prior to this invention, had various defects. Whensome of them were exposed to conditions encountered during use, thegrit-bonding or binder coat would loosen from or shell off of thefibrous backing, This condition might be due to poor adhesion betweenthe binder coat and the backing and/or to a tendency of the fibrousbacking to become. raggif and to stretch out or otherwise undergo changefrom its original dimensions, for example, due to fluids encounteredduring use or because of poor adhesion between the binder coat andimpregnated Various employed, which it is an object of this invention toovercome.- For example, abrasive belts were employed prior to thisinvention, of a type which have been known for upwards of twenty fiveyears, in the polishing or smoothing of glass Yitrolite" and the like,but such belts could only be used dry, which occasioned a serious dustand silicosis hazard. Such prior art belts, which were frequently made.with a glue bond, had the further disadvantage that the gluegrit-bonding coat would soften with heat and hence such articles weresubject to rapid loss of cut" under the high heats often developed indry sanding. This grave disadvantage has been overcome by the wetabrasive belts herein described and illustrated.

In the making of abrasive belts, according to a preferred aspect of thisinvention, the wovenordinary temperatures of use are especiallycontemplated. Illustrative of this class of materials are:polymerization products of ethylene linkage compounds, and of certainother multi-bond carbon to carbon linkage compounds, for example variouspolymeric vinyl compounds of the waterproof or water-dispersible types:sulphur-olefin material. Another obiect is to provide abrasive soresins, e. g. polyalkylene polysulphide resins produced, for example, bythe reaction of ethylene dichloride on sodium polysulphide (Nazsaa).

.such as those employed in making materials such as the commercialproduct Revolite," though the latter is less advantageous than, forexample, various vinyl resins and polyalkylene polysulphide resins inthe making of wet sanding belts for ,glass and the like according tothis invention..' Materials-of the types indicated above may be usedalone as'a backing treatment or impregnating coat for fibrous belts orthe like or may be employed in admixtures. Admixtures containingmaterials of each of the above types have been employed and alsoadmixtures of materials of the above types with other materials not thusfar mentioned, including other resinous or polymeric materials and/orsolvents, plasticizers, modifiers and stabilizers, have been used forthe purposes indicated.

Where materials of the above type are used as a backing coat or as animpregnating coat, a phenolic resin such as a condensation product ofphenol and formaldehyde, or cresol '(or other substituted phenolicmaterial) and an aldehyde, or alkyd modifications of phenol-aldehydesmay be used to advantage as the grit-bonding or binder coat, althoughother materials such as alkyds, urea-aldehydes, etc., may, if desired,be used in combination with or in lieu of phenol-aldehyde resins.

The invention will be further illustrated by the following specificcompositions adapted for use as an impregnating or backing coat orsizing for fibrous materials, e. g. for woven backing materials such ascommercial drills or other suitably woven fabric, such as jeans, wherecloth backing is employed. Drills or other fabrics, woven so as toreduce stretching thereof to a minimum, 1. e. so as to make the samestretchresistant, are especially desirable in making abrasive belts.

The vinyl copolymer mentioned in the above table was made from a mixturecontaining '75- 85% vinyl chloride, the balance being made up primarilyof vinyl acetate. However other proportions vof vinyl chloride and vinylacetate can be employed. Increased quantities of the acetate wouldfurther soften the copolymer.

Other specific vinyl resin compositions contemplated by me for use as animpregnating or backing coat or sizing coat for fibrous material includepolymerization products of vinyl chloride CH2=CHC1, vinyl acetateCH2=CH(C2H3O2), schlor-propylene CH2=CCl.CHa, vinyl alcohol CH2=CHOH andvinyl benzene, etc.

The above compounds have the general formula RCH=CHR', where R. may behydrogen and R. may be a hydroxyl, carboxyl, chloride, acetate, bromide,etc., or various other organic radicals: Where one R in the aboveindicated formula, for example R, is an hydroxyl group,

pounds contained in such a. resinified or polymerized product containshydroxyl groups, this resulting polymerized material is self-dispersibleor where a substantial or high proportion of comor soluble in water.Water solubility or dispers ibility is also promoted by groups otherthan the hydroxyl groups, for example, by the carboxyl (COOH) group orthe amine (NI-I2) group. Where a water-soluble resin is employed, it maybe treated with physical and/or chemical insolubilizing agents toimprove the finished abrasive article or render the samewater-resistant.

Another specific polymerized or resinified product suitable for mypurpose may be made from the following:

Example 2 Parts by weight Vinyl chlm'irlp 30 Vinyl acetate 20 Themixture of Example 2 is properly polymerized, i. e. polymerizedsufllciently so that the resulting product will be a solid of desiredflexibility. Such a polymerized product, which is 'a flexible solid atroom temperatures, may be' Example 3 5-15 parts to a. mixture ofpolymerized vinyl chloride and vinyl acetate made in accordance withexample 2-.

1-10 parts of modifier or plasticizer, e. g. dibutyl phthalate.

The composition of Example 3, when plastic or while still Warm, may bedirectly applied to a backing material such as cloth or the like, asherein otherwise illustrated, for a sizing, filler, sealing orimpregnating coat, for example. The composition of Example 3 may,however, advantageouslybe thinned with volatile organic solvents orvehicles in which such polymerized or resinified mass may be considereda dispersion or solution.

A polymerized or resinified compound, such as the vinyl resin justindicated, may be dissolved in a solvent or thinner mixture asillustrated by the following:

' Parts Butyl ace 40 Ethyl alco 20 Toluene 40 selves and/or with otherphysical and/or chemi- An example of another contemplated composition isas follows: I

black, bone black, zinc oxide, etc.- 2-1 The solvent used with the aboveand the quan- 1} titles thereof may be as indicated in connection withExample 3 hereof, though vehicles altered to produce a dispersion of thepolymerized or resinified products are also contemplated. Vegetableoils, especially those of a drying nature are preferably not used wherea woven, cloth backing is employed and where the finished article is tobe employed for severe duty, such as the sanding of glass, etc. v

Where aqueous mixtures of water-dispersible or soluble vinyl resins, e.g. polyvinyl alcohol etc., as heretofore indicated, are employed inimpregnating a cloth or other fibrous or cellulosic backing, to whichimpregnated backing-a layer of a phenol-aldehyde resin or other suitableor heat convertible resinous or grit-bonding coat is Joined in integralrelation, the waterproofness of such product may be improved by theemployment of suitable modifying agents in conjunction with polyvinylalcohol, e. g. by employing modifying agents such as various vegetableoils including linseed oil, tung oil, etc., as wellas other materials,including paint pigment such as litharge, preferably in combination withlinseed oil, tung oil or the like. The flexible abrasive articles may betreated with such modifying agents after the grit-bonding coat has beenapplied or the abrasive belts or other abrasive articles may be given abacksize treatment with such modifiers before or after the grit-bondingcoat, such as phenolaldehyde, orother heat-convertible or thermoplasticmaterial is applied. The phenol-aldehyde or like grit-bonding coat,together with a suitable or like wa'ter-dispersible impregnating orpresizing coat by keeping water out of contact therewith. Alsowater-dispersible vinyl resins, such as polyvinyl alcohol and the likecan be rendered insoluble or resistant to attack by water, in respect touses to which the article is to be put, by treating the polyvinylalcohol or the like (after the same has been applied to the cloth orlike backing material) with other physical insolubilizing agents aloneor with mixtureshereinabove presented and/or with chemicalinsolubilizing agents such as diethyl sulphate, dimethyl sulphate, etc.in admixture with alkaline material such as caustic alkali; variousethers, ketones such as diethyi ketone, etc. Diethyl sulphate ispreferred over dimethyl sulphate from the angle of safety in use.

Also such modifiers as linseed oil, tung oil, with or without additionagents such as paint pigments, e. g. zinc oxide, lithar'ge, etc., mayalso be ca] insolubilizing agents, herein illustrated, to improve thewater-resistance or waterproofness of abrasive articles made withpolyvinyl alcohol, or other water-dispersible resins, where the latterare used, for example, as a binder or gritbonding coat and/or as asandsizing coat. Such modifiers, for example in oxidized and/orpolymerized state provide waterproof films which, of cfurse, improve thewater-resistance of the abras ve. I

Another composition which may be used as an impregnating or sizing orbacking coat follows.

' Ezcample 5 Parts by weight Oleflne-polysulphide resin (1. e.polyalkylene polysulphide resin) l0 Crepe rubber 5 Zinc oxide 1 Carbonblack 2 Tetra-methyl thiuram disulphide (sof-' tener) .03

Illustrative of specific polyalkylene-polysulphide resins mentioned inExample 5 are reaction products of ethylene dihalide with sodium poly-isulphide. to yield resins'such as' one having the empirical formula,(CzHaSQfl or so-called .Thiokol B, which latter is a product ofcommerce. This type of material isprdinarily not applied to fabrics inthe manner in which vinyl resins may be employed." That is, mostolefine-polysulphide resins, i. e. polyalkylene polysulphine resins,cannot satisfactorily be dissolved. The usual practice is to soften thecomposition, such as above illustrated, usually on a rubber mill, andthen friction it into the cloth or fabric on calender rolls, which atone and the same time stretch the fabric longitudinally andiron down thefibers thereof while coating or impregnating the fabric with acomposition such as illustrated in Example 5. Thus the stretch of thefabric is set, the impreghating or backing coat is applied and the sheetof fabric is calendered all in the one operation. This type ofcomposition and coating operation sets' the stretch of the fabric verysatisfactorily.

Where a bonding or abrasive binder coat of the nature of insolubilizedglue, bonds made with casein, and certain other natural and syntheticresins, or'the like, are used, which adhere with great tenacity to acloth backing, it is often preferred to apply the composition of Example5 only to one surface of the cloth .or fibrous backing material, so asto leave a starved side to which the abrasive binder coat may beapplied. Tension on the backing material is preferably released prior tothe application of the binder coat and the abrasive grits. Any desiredsand-size or grit-size coat may then be applied to the compositeabrasive article and the latter subjected to curing temperatures of theorder of 150 F. to 300 F.,

for a relatively short time sufiicient to effect the curing, withoutdecomposing or embrittling the thermoplastic composition or appreciablydeteriorating the fabric. However temperatures above about 325 or 350 F.are preferably avoided in many if not most instances.

Where grit-bonding coats are employed which will adhere'more firmly to afabric covered with the composition of Example 5 or that of any of theprecedingexamples, according to primarily contemplated aspects of thisinvention, rather used, either alone or in admixtures with themthan to astarved side of the fabric, it will be understood that the above fabricmay be and preferably is thoroughly impregnated with the abovecomposition, or that such composition may. be appii d to both sides ofthe fabric in the manner abofire described or in any other suitablemanner.

While insolubilized glue, etc. are mentioned above as a possiblegrit-bonding coat, it will, of course, beunderstood that phenol-aldehyderesins and other materials mentioned hereinabove, particularly those ofthe heat-convertible type, are especially contemplated for this purposewhere a composition as given in Example 5 is employed as an impregnatingor backing coat.

Another method of producing an impregnated backing sheet, to which asuitable phenol-aldehyde. urea-aldehyde, etc., resinous grit-bondingcoat may be ioined in the making of "wet belts" for glass sanding," orthe like, is as follows:

Take straight phenol and formaldehyde and react the mixture, atsuperatmospheric temperatures (e. g. 180 to 210 F. more or less) and inthe presence of phosphoric acid as catalyst. until a viscous liquid, 1.e. a partly reacted resin, is produced. Then add this viscous liquid toChina-wood oil, intimately admix the same, and

heat to gelation. This gelled material is then milled on a heated rubbermill to further increase the body thereof, or to stiffen the same, andpigments (which may be quite inert) such as zinc oxide, carbon black,litharge, etc. or mixtures containing one or more of the-same, are addedand the milling and heating is continued until the desired plasticity isattained, e. g. until the finished product resembles crepe rubber. Thisplastic product may then be applied to a cloth or fibrous backing, suchas "drills" or Jeans, for example by frictioning the same into thecloth. A suitable grit-bonding coat (or preslze and grit-bonding coat)such as a suitable phenolaldehyde resinous grit-bonding coat may then beapplied to such an impregnated back, and the abrasive grits andsand-sizing coat added thereto, to make a finished article.

While such article is useful and advantageous in making abrasive or likearticles, as illustrated, vinyl resins and/or polyalkylene polysulphideresins, or the like, as hereinabove exemplified, are preferred toimpregnate the backing in making wet belts" for glass sanding and thelike.

In making articles such as abrasive belts, which are often subjected toheavy service requirements and severe stresses, as in the wet sanding"of glass, there are relatively few ma-- terials which can besatisfactorily employed in impregnating the cloth or fibrous backingmaterial 'in the making of a good, serviceable and commerciallyadvantageous article. ins, such as those hereinabove set forth, areexcellent materials for this purpose, particularly when a coating of aphenol-aldehyde resin or a modified phenolic aldehyde resin is appliedin contiguous relation with the polymeric vinyl compound or with thefabric impregnated therewith. This situation exists where the fabric isimpregnated or saturated with a vinyl resin and then is given a presizecoating of the same or another vinyl resin, the phenol-aldehydecondensation product or resin being applied over the vinyl presizecoating. Likewise, a good bonding between a vinyl resin and aphenol-aldehyde resin occurs where, for example, both the presize andgrit-bonding coat are of the phenolaldehyde resin type and the fibrousbacking is first coated or impregnated with a vinyl resin. Among thevinyl resins preferred are mixtures or copolymers comprising polyvinylchloride Vinyl reswhich ar not too high m polyvinyl chloride. Where thelatteris employed, a polyvinyl ester of an organic acid, e. g. polyvinylacetate, or equivalent, is preferably employed to substantial extent.But it is to be understood that polyvinyl chlorideis not required andvinyl resins containing no polyvinyl chloride and no polyvinyl acetateare, of course, contemplated, as

will be seen from description given hereinabove.

However, as will be clear from the description herein taken as a whole,a good final product is also obtained where other types of backing,

treatments or impregnating agents of the type hereinabove described, e.g. various polyalkylene polysulphide type resins, are employed. Aphenol-aldehyde type bonding coat may be employed with satisfaction withany of the impregnating coats above mentioned. Also, other bonding costssuch as alkyds or modified alkyds may be.

employed, although bonding agents containing or comprisingphenol-aldehyde type resins or similar heat-convertible resins are inmost cases preferred by me in the making of abrasiv articles. This isespecially true in the making of "wet belts" for the "sanding of glassor the like. Likewise while the present invention is of high utility inconnection with articles comprising woven fabric backings, it hasutility in connection with other fibrous bodies such as paper, where thefibers are felted rather than woven, although it has very importantutility in connection with wovenfibrous material.

While various phenol-aldehyde resins and other heat-convertible resinsmay be employed as the grit bonding coat (and/or as a presize or as thesandsize coat), as will be understood, the following is illustrative ofan advantageous resin and a method of making the same.

Heat the mixture between about and F. until the formaldehyde percentagehas been lowered to approximately 5 per cent. This may take about 24hours, more or less. Then neutralize the mixture with an acid, e. g.HCl. Next boil oil the water by heating to about 215 F. and hold at thistemperature until the viscosity of the resin is about 500 centipoises at70 C. (150 F.). Now cool to about 200 F. and then add 2.5% by weight of28% aqueous ammonium hydroxide. Hold the temperature of the mixture atsubstantially 200 F. until the viscosity thereof becomes about 1000centipoises at 70 C. Then add solvent, e. g. Cellosolve, and cool toabout 120 F. The amount of Cellosolve, or the like, may be about 10%,more or less. The'resulting resinous material may be used as agrit-bonding coat or, upon further dilution, as a sandsizing orgrit-sizing coat. Where grit sizes Nos. 24, 30 or 36 are employed, thedilution of the resin provided by 10% Cellosolve usually will make thesame satisfactory for a grit-bonding coat, but greater dilution willcustomarily be desired for a sandsizing coat, or as a grit-bonding coatwhere smaller abrasive 'grits are used. On the other'hand, less dilutionis needed where the resin monium hydroxide with sodium hydroxide in thecoat, a layer of granules or abrasive particles of above procedure.

Another advantageous modification of the above procedure, e. g. inproducing a sandsize resin which may be used in making "wet belts" forglass sanding, involves increasing the amoimt of formaldehyde inrelation to the phenol so that the moi ratio is about 2:1. This may beaccomplished by using some paraformaldehyde to avoid excessive water inthe mix. Also, instead of eliminating water by heating up to about 215F., as indicated in the above procedure, the water may be removed byvacuum dehydration at relatively low temperatures. In this modificationalso, sodium hydroxide may be employed instead of ammo'nlum hydroxide.The result is a resin which, when employed.for example, as a sandsizecoat in making an abrasive belt (such as herein illustrated for the wet"sanding of glass, etc.) produces an abrasive article having greaterheat resistance and increased tensile strength and one which will cutconsiderablymore before it is exhausted.

The above are only exemplary of various gritvbonding and/or sandsizingcoats which may be employed. Other resinous materials of suitablecharacter, including urea-aldehydes, alkyd modifled phenollcs, etc.,are. of course, also contemplated.

Where phenolic materials other than phenol are employed as reactants foraldehydes to produce resin grit-bonding coats, it is to be observed thatsome are better than others. For example, various cresols or cresylicacids may be used and, of these, metacresol, paracresol and especiallymeta-paracresols are among the more advantageous reactants for aldehydessuch as formaldehyde.

While the inventio has been illustrated hereinabove in considerabledetail in connection with the making of abrasive sheet goods,particularly such as abrasive belts, e. g. those used in the wetabrading of glass, metal, it will be understood that the invention isnot to be limited by the illustrations. For example it will berecognized that a composite article of this process would have utilityeven though the solid particles embedded in the grit-bonding coat werenot intended for abrading operations. Furthermore it will be recognizedthat sheet goods'can be made up in accordance with the teaching hereinpresented where no granules or like hard particles, whether of adecorative or other nature, are embedded in the surface coating, andwhether or not Fibrous backing described herein, while ordinarilydesired, particularly in abrasive articles such as abrasive belts, isusually employed primarily for the purpose of adding strength andendurance to the finished article. Where the finished article hassufilcient strength for purposes desired in the absence of the fibrousor cloth backing, it will be understood that the same may be dispensedwith while still following the teaching of this invention, for examplein regard to the matter of securing good adhesion or a good bond betweena base or backing coat or layer and a contiguous overlying sheet orbinder coat, as the case may be.

While hereinabove an abrasive article has been discussed comprising afibrous backing material, an impregnating or backing coat therefor, apresize coat, a back-size coat, a grit-bonding or binder coat adapted tobe applied over the presize the like embedded in said binding coat and asandsize or abrasive-size coat over the layer of granules or particles,yet nevertheless it will be understood that this invention is by nomeans limited to such a specific illustration and comprehends compositearticles comprising a plurality of layers of material joined together inaccordance with the teaching of this invention whether they have such anumber or variety of layers or coatings, or not. For example thebacksize coat. the presize coat, and/or the sandsize coat might beabsent. whilestill making a composite article comprising an impregnatedfibrous backing to which a grit binder coat was joined in integralor'contiguous relation. These and other variations within the scope ofthe appended claims are contemplated.

What I claim is: p

1. A flexible abrasive article adapted to be used wet for abrading orpolishing glass, marble and the like which comprises a strong wovenfibrous I material; an impregnating or sizing coat for said fibrousmaterial which consists-of a film-forming, elastic waterproof adhesivematerial comprising a thermoplastic syntheticmesin; a waterproof organicgrit-bonding coat comprising a heat-convertible phenolic-aldehyde resin,Joined to the impregnated fibrous backing aforesaid: and a multiplicityof abrasive particles embedded in said grit-bonding coat; saidgrit-bonding coat being less flexible and very substantially harder thansaid impregnating or sizing coat.

2. A flexible abrasive article comprising a sheet of fibrous materialand at leasttwo layers or coatings of material, all joined in integralrelation, one of said'coatings being an abrasive-bonding coat andanother of said coatings intervening to substantial extent between saidabrasive-bonding coat and said fibrous material and being composed of .asubstance comprising a polyalkylene poly-sulphide resin of a rubberynature, said abrasive-bonding coat comprising a heat convertiblesynthetic resin, and a layer of abrasive in integral relation gritsembedded in said grit-bonding coat.

3. A flexible abrasive article of the coated abrasive type, adapted foruse wet in the abrading or polishing of glass, comprising a fibroussheet, an impregnating or sizing coat for said fibrous sheet comprisinga thermoplastic polyvinyl compound, an organic binder coat joined inintegral relation with the impregnated fibrous sheet aforesaid, and

a multiplicity of abrasive particles anchored by said binder coat, saidorganic binder coat being the latter comprises a phenol-aldehyde resinor of composition diff r t from said impregnatmg other modified orequivalent material.

or sizing coat and comprising a heat-advancing synthetic resin, saidbinder coat being substantially harder than said impregnating or sizingcoat.

4. An abrasive article comprising a fibrous sheet, an impregnating orsizing. coat for said fibrous sheet comprising a thermoplastic polyvinylcompound, an organic binder coat joined with the impreg ated fibroussheet aforesaid, and a multiplicity of abrasive particles anchored bysaid binder coat, said organic binder coat being of compositiondifferent from said impregnating or sizing coat.

. 5. An abrasive article comprising a fibrous sheet, an impregnatingcoat for said fibrous sheet comprising an elastic waterproofthermoplastic copolymer of a vinyl halide and a vinyl ester of anorganic acid; an organic binder coat, which is harder and less flexiblethan said impregnating coat, Joined to the impregnated fibrous sheetaforesaid: and a multiplicity oi abrasive particles embedded in'saidbinder coat.

6. An abrasive article comprising a fibrous sheet. an impregnating orsizing coat for said fibrous'sheet comprising a thermoplastic polyvinylcompound, an organic bindercoat Joined in integral relation with theimpregnated fibrous sheet aforesaid, and a multiplicity oi abrasiveparticles anchored by said binder coat, said organic binder coat beingor a composition difierent from said impregnating or sizing coat andcomprising a heat-convertible phenolic resin, said bindercoat beingharder and less flexible than said impregnating or sizing coat.

7. An abrasive article comprising a fibrous sheet, an impregnating orsizing coat for said used wet for abradingand smoothing glass. steelfibrous sheet comprising a thermoplastic polyvinyl compound. an organicbinder coat ioined in integral relation with the impregnated fibroussheet aforesaid. and a multiplicity oi abrasive particles anchored bysaid binder coat. said binder coat being oi composition diiierent tromsaid impregnating or sizing coat and comprising a heat-advancing phenolaldehyde resin, said binder coat being harder than said impregnating orsizing coat.

and like heavy abrading operations which com prises a strong woven,stretch-resistant fibrous material: an impregnating or sizing coat iorsaid fibrous material which comprises a waterproof, thermoplasticresinous organic material containing a vinyl resin and a polyalkylenepolysulphide resin or a rubbery character: a grit-bonding or binder coatwhich is harder and less fiexible than saidimpregnating-coat andcomprises a heatadvancing synthetic resin, overlying and Joined inintegral relation with the impregnated fibrous backing aforesaid; and amultiplicity of abrasive particles embedded in said grit-bonding coat.

10. A flexible abrasive article comprising a sheet oi-fibrous materialand at least two layers or coatings of material, all Joined in integralrelation, one of said coatings being an abrasivebpnding or binder coatcomprising a heat convertible phenolic resin and another of saidcoatings intervening to substantial extent between said abrasive-bondingcoat and said fibrous material and being composed or a substance com- 8.A flexible abrasive article of the coated I abrasive type, adapted to beused wet in the sanding or glass. marble and the like. comprising afibrous sheet backing material. an impregnating or sizing coat for saidfibrous sheet comprising a thermoplastic polyvinyl ester 0! an organicacid, an organic binder coat joined in integral relation with theimpregnated fibrous sheet aforesaid, and a multiplicity of abrasiveparticles anchored by said binder coat, said organic binder coat beingoi composition different from said impregnating or sizing coat andcomprising a heat-convertible phenolic realm 9. A fiexiblev abrasivebelt 'adapted to be coat.

BYRON J. CAKES.

CERTIFICATE OF conmzqnox. Patent no. 2, 57, 50,

September 5, 19141;.

BYRON J. CAKES.

It is hereby certified that error appear: in the printed specificationor the above numbered patent requiring correction ae toll'ovya: Page 1,sec- 0nd column, 11mm, for "nautral' read --naturaI--' page 2, ee'condcolumn,

line 1 for the word 'purpoeel' read -purpoeev-f line 11,0, for "5-15parts I read 5-25 parts": page}, second column, line 53 for"poiyeulphine" read po1yeu1ph1de--;'page' 5, second column, line 1, for"of" arter'fparticles' read --er.----;v and; that the said Lettere-Patent should be read with this correction therein that the eeme nayconform to the record of the case in the Patent Office;

Signed and sealed this 26th day or December; A. 1). 191m.

Leslie Frazer I v I e (Seal) Acting Commissioner of Patents.

